The parts I am using are mainly from a company called ServoCity. This is the first time I have used any parts from them, and so far, I can highly recommend what I have seen. Sparkfun also approves of their products.
Anyway, the arm consists of two 15 inch channels from ServoCity, and three 1/4 scale winch servos, geared down to have more torque. When it is all built, I expect the arm to be able to lift three to five pounds, fully extended. I've done some tests so far, and it seems to be meeting this expectation. The entire thing is controlled by an Arduino Mega, running FINF (a Forth implementation), which allows me to experiment with the arm really quickly.
Here it is, running through a test sequence: